Removal of hard COD, nitrogenous compounds and phenols from a high-strength coal gasification wastewater stream

The objective of this study was to identify the factors affecting the suspended and fixed biomass in the removal of hard COD, nitrogenous compounds and phenols from a coal gasification wastewater (CGWW) stream using a hybrid fixed-film bioreactor (H-FFBR) process under real-time plant operational conditions and actual wastewater composition. The composition of the influent and effluent was studied to determine which compounds were not removed by hydrolysis (bacterial activity) and how this correlated to the suspended and fixed biomass activity, COD and phenol removal. A H-FFBR with 12 g∙m−3 attached biomass and 440 mg∙ℓ−1 suspended biomass achieved 78% phenol removal and 49% COD removal but insignificant removal of nitrogenous compounds. During the operation period, fixed biomass concentration was higher than the suspended biomass. Parameters such as pH, phenols, alkalinity, metal ions, conductivity, total dissolved solids and aeration rate affected the fixed biofilm properties such as adhesion, thickness and structure. It can be concluded that the composition of the effluent had a direct effect on the fixed biomass properties and thus a direct effect on the removal of phenols, COD and nitrogenous compounds in the wastewater.The authors would like to thank Buckman Africa for funding the chemical, EDX, GC-MS and SEM analyses and Sasol Technology (Pty) Ltd for the use and operation of the pilot plant.http://www.wrc.org.zaam201

Removal of hard COD, nitrogenous compounds and phenols from a high-strength coal gasification wastewater stream

The objective of this study was to identify the factors affecting the suspended and fixed biomass in the removal of hard COD, nitrogenous compounds and phenols from a coal gasification wastewater (CGWW) stream using a hybrid fixed-film bioreactor (H-FFBR) process under real-time plant operational conditions and actual wastewater composition. The composition of the influent and effluent was studied to determine which compounds were not removed by hydrolysis (bacterial activity) and how this correlated to the suspended and fixed biomass activity, COD and phenol removal. A H-FFBR with 12 g∙m−3 attached biomass and 440 mg∙ℓ−1 suspended biomass achieved 78% phenol removal and 49% COD removal but insignificant removal of nitrogenous compounds. During the operation period, fixed biomass concentration was higher than the suspended biomass. Parameters such as pH, phenols, alkalinity, metal ions, conductivity, total dissolved solids and aeration rate affected the fixed biofilm properties such as adhesion, thickness and structure. It can be concluded that the composition of the effluent had a direct effect on the fixed biomass properties and thus a direct effect on the removal of phenols, COD and nitrogenous compounds in the wastewater.The authors would like to thank Buckman Africa for funding the chemical, EDX, GC-MS and SEM analyses and Sasol Technology (Pty) Ltd for the use and operation of the pilot plant.http://www.wrc.org.zaam201

The use of exogenous microbial species to enhance the performance of a hybrid fixed-film bioreactor treating coal gasification wastewater to meet discharge requirements

The objective of this study was to determine whether inoculating a hybrid fixed-film bioreactor with exogenous bacterial and diatoma species would increase the removal of chemical oxygen demand, nitrogenous compounds and suspended solids from a real-time coal gasification wastewater to meet environmental discharge requirements specified for petrochemical refineries. The COD removal increased by 25% (45% to 70%) at a relatively high inoculum dosage (370 g∙m−3) and unit treatment cost (12.21 €∙m−3). The molar ratio of monovalent cations to divalent cations (M/D >2) affected nitrification, settling of solids and dewatering of the sludge. The use of a low-charge cationic flocculant decreased the suspended solids in the effluent by 70% (180 mg∙L−1 to 54 mg∙L−1) and increased the sludge dewatering rate by 88% (61 s∙L∙g−1 to 154 s∙L∙g−1) at a unit treatment cost of 2.5 €∙t−1 dry solids. Organic compounds not removed by the indigenous and exogenous microbial species included benzoic acids (aromatic carboxylic acids), 2-butenoic acid (short-chain unsaturated carboxylic acid), I(2H)-isoquinolinone (heterocyclic amine), hydantoins (highly polar heterocyclic compounds), long-chain hydrocarbon length (carbon length > C15) and squalene. These organic compounds can thus be classified as poorly degradable or nonbiodegradable which contributed to the 30% COD not removed by the H-FFBR. The use of exogenous microbial species improved the quality of CGWW; however, not sufficiently to meet discharge requirements. The cost of such treatment to meet discharge requirements would be unsustainable. Alternative technologies need to be investigated for reusing or recycling the CGWW rather than discharging.The authors would like to thank Buckman Africa for financing the chemical and microbiological analyses and Sasol Group Technology (Pty) Ltd for the use and operation of the pilot plant.http://www.wrc.org.zaam2016Chemical Engineerin